Study the impact of liner thickness on the 0.18 mu m devices using low dielectric constant hydrogen silsesquioxane as the interlayer dielectric

The electrical performance of hydrogen silsesquioxane (HSQ) as the interlay er level dielectric (ILD) has been determined by using two-metal-layered te st structures to study the impact of oxide liner thickness on the capacitan ce reduction. In comparison with SiO2, HSQ test structures formed with SiO2 cap and liner or with SiO2 cap only, have 20-27% lower intraline capacitan ce while 6-16% reduction was observed for fluorosilicate glass (FSG) relati ve to SiO2. It was found that the capacitance of SiO2/HSQ ILDs did not vary with oxide liner thickness as expected. Similar effects were observed with via resistance measurement. Analysis of the structure shows that wide vari ation of SiO2/HSQ/SiO2 stack thickness after oxide Chemical Mechanical Poli shing (CMP) step changed the expected contribution of liner thickness on th e intraline and interlayer capacitance. This thickness variation also has a strong impact on landed/unlanded via resistance. Therefore, a good control of oxide CMP on the ILD stack is needed to reduce the thickness variation of the liner/HSQ/cap ILD stack which in turn will enhance process yields in the 0.18 mum devices. (C) 2000 Elsevier Science B.V. All rights reserved.